I have yet to see wing chun effectively used in any competition. Come to Portland and workout, internet guru.

Sigh. MT is clearly a serious art with a long history of successes. Nearly all schools I've heard of practice a really serious conditioning routine and hard/full-contact sparring. That's great.

Some WC schools do it that way too. The ones that do have produced some reasonable MMA competitors (search for the vid of Dochter's teacher competing, google on Kevin Chan of London, UK).

I've never heard of a quality WC school that claims chain punches are an ultimate, fight-ending power technique.
They are useful for keeping an opponent 'on the back foot' by keeping something coming at his face which makes it hard for him to get his guard back together and keeps him backing up while you set him up for something more serious. When going for a knockdown, most WCers I know have been taught to elbow to the side of the head, palm to the face or sweep/low-kick intended to take the legs out from underneath.

WC kicks clearly aren't devastating in competition the way MT kicks have been. Most of them are usually used as a way of getting into range to attempt some kind of sweep.
The WC kick where you kick the opponents shin with your heel is a lot more painful when you're wearing sturdy outdoor shoes. Most people don't have conditioned shins like a professional MT fighter.

it just body mechanics no? WC chain punching looks like it's all arms and has very little bodyweight behind them.

Is this because they are trying to maintain the WC stance and protect the centerline?

In the case of chain punches in particular, I've been taught that these are best used to keep somebody distracted and disrupting their guard by constantly jabbing at their face whilst you work in closer to deliver something more substantial, like an elbow to the head, or kicking their legs from under them.

That said, all WC hand techniques (including elbows) are supposed to be driven from the hips for power.
One of the things I was most commonly picked up on in my first six months of WC was that I was throwing punches just using my arm, and not putting my whole body into it. You're also taught to step into people as you hit them. The body-mechanics that you're trying to get right in WC is the ability to use some of the force generated by your legs and hips when you punch people, rather than just the muscles in your arm and shoulder. Couple this with the fact that you're trying to do this whilst maintaining a steady balance (in WC, your told to do this keeping your body vertical if at all possible) and keeping your centrline as covered as possible , with both hands ready to strike, and you have the basic reason that WC stances and forms look the way they do.

Learning to generate power with a twist of the hips is the reason the second form is full of repetitive movements where you turn yourself from side to side by driving yourself round with your hips.
Of course, good WC schools don't rely on just the forms to teach this. You're also supposed to hit bags and spar with hard contact. However, I did find trying to do the second form helpful for getting the basic mechanics of hip movement right before adding in the extra condusion and adrenalin of a live opponent.

One thing I've _never_ done been made to do at my school, which seems really common in other WC clubs, is to spend lesson after lesson doing chain-punches in the air in a static stance as part of a standard warm-up.

In the case of chain punches in particular, I've been taught that these are best used to keep somebody distracted and disrupting their guard by constantly jabbing at their face whilst you work in closer to deliver something more substantial, like an elbow to the head, or kicking their legs from under them.

That said, all WC hand techniques (including elbows) are supposed to be driven from the hips for power.
One of the things I was most commonly picked up on in my first six months of WC was that I was throwing punches just using my arm, and not putting my whole body into it. You're also taught to step into people as you hit them. The body-mechanics that you're trying to get right in WC is the ability to use some of the force generated by your legs and hips when you punch people, rather than just the muscles in your arm and shoulder. Couple this with the fact that you're trying to do this whilst maintaining a steady balance (in WC, your told to do this keeping your body vertical if at all possible) and keeping your centrline as covered as possible , with both hands ready to strike, and you have the basic reason that WC stances and forms look the way they do.

Learning to generate power with a twist of the hips is the reason the second form is full of repetitive movements where you turn yourself from side to side by driving yourself round with your hips.
Of course, good WC schools don't rely on just the forms to teach this. You're also supposed to hit bags and spar with hard contact. However, I did find trying to do the second form helpful for getting the basic mechanics of hip movement right before adding in the extra condusion and adrenalin of a live opponent.

One thing I've _never_ done been made to do at my school, which seems really common in other WC clubs, is to spend lesson after lesson doing chain-punches in the air in a static stance as part of a standard warm-up.

The principal as i was taught was as you said the footwork generates the power by turning into or with the strike... not sure what this ongoing business about the chain punch is,, i was taught its a tool to teach you not to stop.... every movement comes through the centre line so your pretty much already blocking you just move through centre to bon or garn, and there is your block, plus you use the blocks as strikes also in a continuos motion, the chain punch is just the beginning step,, just a beginners tool to understand your body positioning and how you move, to teach you timing when you have to change a strike to a block use footwork, but why not also strike with the block, you can still use your other arm and a leg as well at that range to strike... ignoring the bill gee if you look at every block, bill so for eg.. its and outside edge of hand thrust block or strike, generaly taught as defense against high kicks or round punches, you can use it as a strike anywhere from waist to head hight. Bon sao depending on you range can be an edge of hand strike, an forearm strike or an elbow. Whats more the staight forward movement when used with footwork means you for eg diverting the straight punch while striking the person.... The point is to strike of as per the butterfly swords cut, use footwork use the appropriate strike that redirects the attack, then continue as per the principal of the chain punch... there is no defense in wing chun.. but yes everything can be how you want it to be yin or yang